Quasi co-location identification of reference symbol ports for coordinated multi-point communication systems

ABSTRACT

Methods and apparatuses indicate and identify quasi co-located reference signal ports. A method of identifying by a UE includes identifying, from downlink control information, a CSI-RS port that is quasi co-located with a DM-RS port assigned to the UE. The method includes identifying large scale properties for the assigned DM-RS port based on large scale properties for the CSI-RS port. The method includes performing channel estimation and/or time/frequency synchronization using the identified large scale properties for the DM-RS port. Another method for identifying by a UE includes identifying, from downlink control information, a CRS port that is quasi co-located with a CSI-RS port configured for the UE. The method includes identifying large scale properties for the configured CSI-RS port based on large scale properties for the CRS port. The method includes performing channel estimation and/or time/frequency synchronization using the identified large scale properties for the CSI-RS port.

CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 13/866,804 filed Apr. 19, 2013 and entitled “QUASICO-LOCATION IDENTIFICATION OF REFERENCE SYMBOL PORTS FOR COORDINATEDMULTI-POINT COMMUNICATION SYSTEMS,” now U.S. Pat. No. 10,085,202, andclaims priority to U.S. Provisional Patent Application No. 61/635,742filed Apr. 19, 2012 and entitled “METHODS AND APPARATUS TO DETERMINEQUASI CO-LOCATION OF RS PORTS AND DOWNLINK TIMING REFERENCE FOR CoMP”;U.S. Provisional Patent Application No. 61/650,300 filed May 22, 2012and entitled “METHODS AND APPARATUS TO DETERMINE QUASI CO-LOCATION OF RSPORTS AND DOWNLINK TIMING REFERENCE FOR CoMP”; U.S. Provisional PatentApplication No. 61/678,994 filed Aug. 2, 2012 and entitled “METHODS ANDAPPARATUS TO DETERMINE QUASI CO-LOCATION OF RS PORTS FOR CoMP”; U.S.Provisional Patent Application No. 61/680,146 filed Aug. 6, 2012 andentitled “METHODS AND APPARATUS TO DETERMINE QUASI CO-LOCATION OF RSPORTS FOR CoMP”; and U.S. Provisional Patent Application No. 61/699,066filed Sep. 10, 2012 and entitled “METHODS AND APPARATUS TO DETERMINEQUASI CO-LOCATION OF RS PORTS FOR COMP.” The content of theabove-identified patent documents is incorporated herein by reference.

TECHNICAL FIELD

The present application relates generally to Coordinated Multi-Point(CoMP) communication systems and, more specifically, to identificationof reference symbol ports that may be considered as quasi co-located.

BACKGROUND

CoMP technology has been standardized to allow the user equipment (UE)to receive signals from multiple transmission points (TPs) in differentusage scenarios. The different scenarios include: 1) a homogeneousnetwork with intra-site CoMP, 2) a homogeneous network with hightransmit (Tx) power remote radio heads (RRHs), 3) a heterogeneousnetwork with low-power RRHs within the macro cell coverage where thetransmission/reception points created by the RRHs have different cellidentifiers (IDs) from the macro cell, and 4) a heterogeneous networkwith low power RRHs within the macro cell coverage where thetransmission/reception points created by the RRHs have the same cell IDsas the macro cell. The CoMP communication schemes that have beenidentified as the focus for standardization are joint transmission (JT);dynamic point selection (DPS), including dynamic point blanking; andcoordinated scheduling/beamforming, including dynamic point blanking.Further description of the CoMP usage scenarios is included in 3GPP TS36.819, which is expressly incorporated by reference herein.

Accordingly, there is a need for improved techniques in the CoMPcommunication schemes.

SUMMARY

Embodiments of the present disclosure provide methods and apparatuses toindicate and identify quasi co-located reference signal ports in awireless communication system.

In one embodiment, a method for identifying quasi co-located referencesignal ports by a user equipment (UE) is provided. The method includesreceiving downlink control information. The method includes identifying,from the downlink control information, a channel state informationreference signal (CSI-RS) port that is quasi co-located with ademodulation reference signal (DM-RS) port assigned to the UE. Themethod includes identifying large scale properties for the assignedDM-RS port based on large scale properties for the CSI-RS port.Additionally, the method includes performing at least one of channelestimation, time synchronization, or frequency synchronization using thelarge scale properties for the assigned DM-RS port and the CSI-RS port.

In another embodiment, a method for indicating quasi co-locatedreference signal ports by a network entity is provided. The methodincludes providing, in downlink control information for a UE, anindication of a CSI-RS port that is quasi co-located with a DM-RS portassigned to the UE for the UE to identify large scale properties for theassigned DM-RS port based on large scale properties for the CSI-RS portto perform at least one of channel estimation, time synchronization, orfrequency synchronization using the identified large scale propertiesfor the assigned DM-RS port and the CSI-RS port.

In yet another embodiment, an apparatus in a UE configured to identifyquasi co-located reference signal ports is provided. The apparatusincludes a receiver configured to receive downlink control informationand a controller. The controller is configured to identify, from thedownlink control information, a CSI-RS port that is quasi co-locatedwith a DM-RS port assigned to the UE. The controller is configured toidentify large scale properties for the assigned DM-RS port based onlarge scale properties for the CSI-RS port. Additionally, the controlleris configured to perform at least one of channel estimation, timesynchronization, or frequency synchronization using the large scaleproperties for the assigned DM-RS port and the CSI-RS port.

In another embodiment, an apparatus in a network entity configured toindicate quasi co-located reference signal ports is provided. Theapparatus includes a transmitter configured to provide, in downlinkcontrol information for a UE an indication of a CSI-RS port that isquasi co-located with a DM-RS port assigned to the UE for the UE toidentify large scale properties for the assigned DM-RS port based onlarge scale properties for the CSI-RS port to perform at least one ofchannel estimation, time synchronization, or frequency synchronizationusing the identified large scale properties for the assigned DM-RS portand the CSI-RS port.

In yet another embodiment, a method for identifying quasi co-locatedreference signal ports by a UE is provided. The method includesreceiving downlink control information. The method includes identifying,from the downlink control information, a cell-specific reference signal(CRS) port that is quasi co-located with a CSI-RS port configured forthe UE. The method includes identifying large scale properties for theconfigured CSI-RS port based on large scale properties for the CRS port.Additionally, the method includes performing at least one of channelestimation, time synchronization, or frequency synchronization using theidentified large scale properties for the CSI-RS port.

In another embodiment, a method for indicating quasi co-locatedreference signal ports by a network entity is provided. The methodincludes providing, in downlink control information for a UE, anindication of a CRS port that is quasi co-located with a CSI-RS portconfigured for the UE for the UE to identify large scale properties forthe configured CSI-RS port based on large scale properties for the CRSport to perform at least one of channel estimation, timesynchronization, or frequency synchronization using the identified largescale properties for the CSI-RS port.

In yet another embodiment, an apparatus in a UE configured to identifyquasi co-located reference signal ports is provided. The apparatusincludes a receiver configured to receive downlink control informationand a controller. The controller is configured to identify, from thedownlink control information, a CRS port that is quasi co-located with aCSI-RS port configured for the UE. The controller is configured toidentify large scale properties for the configured CSI-RS port based onlarge scale properties for the CRS port. The controller is configured toperform at least one of channel estimation, time synchronization, orfrequency synchronization using the identified large scale propertiesfor the CSI-RS port.

In another embodiment, an apparatus in a network entity configured toindicate quasi co-located reference signal ports is provided. Theapparatus includes a transmitter configured to provide, in downlinkcontrol information for a UE, an indication of a CRS port that is quasico-located with a CSI-RS port configured for the UE for the UE toidentify large scale properties for the configured CSI-RS port based onlarge scale properties for the CRS port to perform at least one ofchannel estimation, time synchronization, or frequency synchronizationusing the identified large scale properties for the CSI-RS port.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise,” aswell as derivatives thereof, mean inclusion without limitation; the term“or,” is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller”means any device, system or part thereof that controls at least oneoperation, such a device may be implemented in hardware, firmware orsoftware, or some combination of at least two of the same. It should benoted that the functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely.Definitions for certain words and phrases are provided throughout thispatent document, those of ordinary skill in the art should understandthat in many, if not most instances, such definitions apply to prior, aswell as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an exemplary wireless system which transmits messagesin accordance with an illustrative embodiment of the present disclosure;

FIG. 2 illustrates a high-level diagram of an orthogonal frequencydivision multiple access transmit path in accordance with anillustrative embodiment of the present disclosure;

FIG. 3 illustrates a high-level diagram of an orthogonal frequencydivision multiple access receive path in accordance with an illustrativeembodiment of the present disclosure;

FIG. 4 illustrates a block diagram of a transmitter and a receiver in awireless communication system that may be used to implement variousembodiments of the present disclosure;

FIG. 5 illustrates a block diagram of a CoMP communication system inaccordance with various embodiments of the present disclosure;

FIG. 6 illustrates a DM-RS and CSI-RS parameter configuration in a CoMPcommunication system according to various embodiments of the presentdisclosure;

FIG. 7 illustrates an example of DM-RS resource and CSI-RS resourcequasi co-location configurations changing over time in accordance withvarious embodiments of the present disclosure;

FIG. 8 illustrates a process for identifying quasi co-located referencesignal ports by a UE in accordance with various embodiments of thepresent disclosure; and

FIG. 9 illustrates another process for identifying quasi co-locatedreference signal ports by a UE in accordance with various embodiments ofthe present disclosure.

DETAILED DESCRIPTION

FIGS. 1 through 9, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably-arranged system or device.

The following documents and standard descriptions are herebyincorporated into the present disclosure as if fully set forth herein:3GPP TS 36.133 V10.3.0 (2011-06); RP-111365 “Coordinated Multi-PointOperation for LTE WID”; 3GPP TR 36.819 V11.0.0 (2011-09); R1-121026“Discussion on Antenna Ports Co-location,” by Ericsson, ST-Ericsson. Thepresent application also incorporates by reference U.S. patentapplication Ser. No. 13/626,572, filed Sep. 25, 2012 and entitled“Downlink Timing Reference for Coordinated Multipoint Communication.”

Standards for CoMP communication include enhancement to DMRS sequencesupported in release 11 for DL-CoMP. The scrambling sequence of DMRS forPDSCH on ports 7˜14 is initialized according to equation 1 below:c _(init)=(└n _(s)/2┘+1)·(2X+1)·2¹⁶ +n _(SCID)  (1)where X is a parameter whose value is dynamically chosen from {x(0),x(1), . . . x(N−1)} for N>1, and x(n) (0<=n<N) are configured byUE-specific radio resource control (RRC) signaling, where N=2, X isjointly indicated with the scrambling identity (n_(SCID)) only for rank1 and 2 in DCI format 2D (nSCID equals to 0 for the rank larger than 2).The scrambling sequence itself can be generated according to 3GPP TS36.211 § 6.10.3.1, which is expressly incorporated by reference herein.

The configuration of multiple non-zero power CSI-RS resources includesat least information elements (3GPP TS 36.331, which is expresslyincorporated by reference herein): AntennaPortsCount, ResourceConfig,SubframeConfig, and the parameter X to derive scrambling initialization(X ranges from 0 to 503, can be interpreted as virtual cell ID, and inrelease 10 of 3GPP is the PCI of the serving cell). The scramblingsequence of CSI-RS is initialized according to equation 2 below:c _(init)2¹⁰·(7·(n _(s)+1)+l+1)·(2·X+1)+2·X+N _(CP)  (2)These parameters are configured per CSI-RS resource. The scramblingsequence itself can be generated according to 3GPP TS 36.211 § 6.10.5.1,which is expressly incorporated by reference herein. Further study hasbeen proposed as to whether some parameters can be configured per CSI-RSport considering the decision of supporting coherent joint transmissionby the aggregated CSI feedback corresponding to multiple TPs in oneCSI-RS resource; UE-specific RRC signaling for CSI-RS restriction isconfigurable per CSI-RS resource; and signaling of the bandwidthinformation for CSI-RS.

A CSI-RS resource can also be configured with an identifier (ID) whichis unique within a set of CSI-RS resources configured to the UE,referred to herein as a CSI-RS resource ID. To distinguish the Xparameter for CSI-RS from the X parameter for DM-RS, the X parameter forCSI-RS is referred to herein as X_(CSIRS), and the X parameter for DM-RSis referred to herein as X_(DMRS). Similarly, to distinguish the n_(s)parameter for CSI-RS from the ns parameter for DM-RS, the n_(s)parameter for CSI-RS is referred to herein as n_(s) ^(CSIRS), and then_(s) parameter for DM-RS is referred to herein as n_(s) ^(DMRS).

A set of RS antenna port(s) (of the same type) can be considered to bequasi co-located by the UE according to predefined rules are provided inTABLE 1 below.

TABLE 1 Example CRS DMRS CSI-RS antenna port groupings antenna portantenna port (per CSI-RS resource) Example 1 (0, 2), (1, 3) (7, 8), (9,10), (15, 16), (17, 18), (suitable for (11, 13), (12, 14) (19, 20), (21,22) interleaved indoor deployments) Example 2 (0, 1), (2, 3) (7, 8), (9,10), (15, 16), (17, 18), (optimized for (11, 13), (12, 14) (19, 20),(21, 22) 2tx non interleaved deployments) Example 3 (0, 1, 2, 3) (7, 8,9, 10, 11, 12, (15, 16, 17, 18, 19, 20, 13, 14) 21, 22) (107, 108, 109,110)

Embodiments of the present disclosure provide methods for UE todetermine which set of RS ports (DM-RS, CSI-RS, and CRS) can beconsidered quasi co-located so that the UE is allowed to derive the“large scale properties” of one RS port, (e.g., properties needed forchannel estimation/time-frequency synchronization based on the RS port)from measurement on another RS port. The large scale properties mayinclude, for example, and without limitation, Doppler shift, Dopplerspread, average delay, delay spread, frequency shift, average receivedpower (may only be relevant for ports of the same type), average gain,and/or received timing. Correctly estimating the large scale propertiescan be important to ensure good channel estimation performance, e.g.minimum mean square error (MMSE) based channel estimator, which mayrequire information, such as the path delay profile estimate (foraccurate frequency correlation estimate), Doppler estimate (for accuratetime-correlation estimate), noise variance, etc. Additionally,embodiments of the present disclosure provide details on signalingrequired to determine the DL timing reference for DL signal receptions(e.g., for CoMP deployment scenarios).

When DL CoMP transmission is configured for a UE, the downlink timingarrival from different TPs can be different due to the unequal distancesfrom the UE to the various TPs.

For the CoMP scenario 3, if the UE is a macro UE (i.e., RRC connected orcamped to the macro eNB/TP), the UE DL timing may be synchronized withthe high-powered macro cell/TP even though a low-powered TP can benearer to the UE. For example, the UE may miss the first transmittedsignal paths from the low-powered TP that can contain significant energybefore the UE DL timing reference according to the farther high-poweredmacro TP. Similarly, for the CoMP scenario 4, the UE may miss the firsttransmitted signal paths from the low-powered TP if the UE also uses theCSI-RS of the macro TP to assist with DL timing synchronization(different TP is assumed to transmit different CSI-RS for thisscenario). As a result, the downlink timing determined by the UE for DLCoMP transmission will be suboptimal, which degrades the performance ofCoMP (e.g., in JT or DPS).

Proposed solutions in U.S. patent application Ser. No. 13/626,572include that when DL CoMP transmission (e.g., JT or DPS) is configured,the DL timing reference for CoMP reception shall be defined as the timewhen (e.g., the first detected path (in time)) of the correspondingdownlink frame is received from the reference cell or reference TP. TheUE may determine the downlink timing of a TP/cell from a referencesignal received from the TP/cell (e.g., the primary synchronizationsignal (PSS), the secondary synchronization signal (SSS), the CRS, theCSI-RS, and/or some other reference signal). Also, a TP may correspondto a CSI-RS configuration (e.g., index tuple of a configuration index, asubframe configuration index, and a number of CSI-RS ports). Analternative for the DL timing reference for the cell/TP includes thatany TP belonging to the CoMP measurement set with the earliest patharrival, min {t1, t2, . . . , tK}, where tk is the path arrival timingfor TP k and K is the number of TPs. One advantage of this arrangementis that the need for additional signaling of the reference TP/cell canbe avoided. For example, the CoMP measurement set is according to thedefinition in 3GPP TR 36.819 V11.0.0 (2011-09) and is configured by RRC.If a TP (i.e., TP A) is chosen among three TPs (i.e., TP A, TP B, and TPC) by the network entity for DL transmission in subframe n (e.g., DPS),but TP C was determined by the UE to have the earliest detected, thedownlink timing reference for subframe n shall be according to TP C. Dueto the semi-static nature of the CoMP measurement set configuration, thetiming reference for the cell/TP may not change in a very dynamicmanner.

An alternative for the DL timing reference for the cell/TP includes thata TP is signaled by the network entity (e.g., from among the DL CoMP set(e.g., from CSI/RSRP measurement) or the UL CoMP set (e.g. from SRSmeasurement)). Advantages of this arrangement include flexibility forthe network entity and simplified implementation at the UE. Optionally,the network entity may also signal the physical signals to be used bythe UE to achieve DL timing synchronization for DL CoMP reception,(e.g., CRS or CSI-RS). Advantages of these embodiments include thatpotentially strong multi-paths from a TP/cell that arrive early at theUE are not missed by the UE in the DL reception for CoMP, therebyimproving the performance of CoMP.

FIGS. 1-3 below describe various embodiments implemented in wirelesscommunications systems and with the use of OFDM or OFDMA communicationtechniques. The description of FIGS. 1-3 is not meant to imply physicalor architectural limitations to the manner in which differentembodiments may be implemented. Different embodiments of the presentdisclosure may be implemented in any suitably arranged communicationssystem.

FIG. 1 illustrates exemplary wireless system 100, which transmitsmessages according to the principles of the present disclosure. In theillustrated embodiment, wireless system 100 includes transmission points(e.g., an Evolved Node B (eNB), Node B), such as base station (BS) 101,base station (BS) 102, base station (BS) 103, and other similar basestations or relay stations (not shown). Base station 101 is incommunication with base station 102 and base station 103. Base station101 is also in communication with a network 130, such as the Internet ora similar IP-based system (not shown).

Base station 102 provides wireless broadband access (via base station101) to network 130 to a first plurality of user equipment (e.g., mobilephone, mobile station, subscriber station) within coverage area 120 ofbase station 102. The first plurality of user equipment includes userequipment 111, which may be located in a small business (SB); userequipment 112, which may be located in an enterprise (E); user equipment113, which may be located in a WiFi hotspot (HS); user equipment 114,which may be located in a first residence (R); user equipment 115, whichmay be located in a second residence (R); and user equipment 116, whichmay be a mobile device (M), such as a cell phone, a wireless laptop, awireless PDA, or the like.

Base station 103 provides wireless broadband access (via base station101) to network 130 to a second plurality of user equipment withincoverage area 125 of base station 103. The second plurality of userequipment includes user equipment 115 and user equipment 116. In anexemplary embodiment, base stations 101-103 may communicate with eachother and with user equipment 111-116 using OFDM or OFDMA techniques.

While only six user equipment are depicted in FIG. 1, it is understoodthat wireless system 100 may provide wireless broadband access toadditional user equipment. It is noted that user equipment 115 and userequipment 116 are located on the edges of both coverage area 120 andcoverage area 125. User equipment 115 and user equipment 116 eachcommunicate with both base station 102 and base station 103 and may besaid to be operating in handoff mode, as known to those of skill in theart.

User equipment 111-116 may access voice, data, video, videoconferencing, and/or other broadband services via network 130. In anexemplary embodiment, one or more of user equipment 111-116 may beassociated with an access point (AP) of a WiFi WLAN. User equipment 116may be any of a number of mobile devices, including a wireless-enabledlaptop computer, personal data assistant, notebook, handheld device, orother wireless-enabled device. User equipment 114 and 115 may be, forexample, a wireless-enabled personal computer (PC), a laptop computer, agateway, or another device.

FIG. 2 is a high-level diagram of transmit path circuitry 200. Forexample, the transmit path circuitry 200 may be used for an orthogonalfrequency division multiple access (OFDMA) communication. FIG. 3 is ahigh-level diagram of receive path circuitry 300. For example, thereceive path circuitry 300 may be used for an orthogonal frequencydivision multiple access (OFDMA) communication. In FIGS. 2 and 3, fordownlink communication, the transmit path circuitry 200 may beimplemented in base station (BS) 102 or a relay station, and the receivepath circuitry 300 may be implemented in a user equipment (e.g. userequipment 116 of FIG. 1). In other examples, for uplink communication,the receive path circuitry 300 may be implemented in a base station(e.g. base station 102 of FIG. 1) or a relay station, and the transmitpath circuitry 200 may be implemented in a user equipment (e.g. userequipment 116 of FIG. 1).

Transmit path circuitry 200 comprises channel coding and modulationblock 205, serial-to-parallel (S-to-P) block 210, Size N Inverse FastFourier Transform (IFFT) block 215, parallel-to-serial (P-to-S) block220, add cyclic prefix block 225, and up-converter (UC) 230. Receivepath circuitry 300 comprises down-converter (DC) 255, remove cyclicprefix block 260, serial-to-parallel (S-to-P) block 265, Size N FastFourier Transform (FFT) block 270, parallel-to-serial (P-to-S) block275, and channel decoding and demodulation block 280.

At least some of the components in FIGS. 2 and 3 may be implemented insoftware, while other components may be implemented by configurablehardware or a mixture of software and configurable hardware. Inparticular, it is noted that the FFT blocks and the IFFT blocksdescribed in this disclosure document may be implemented as configurablesoftware algorithms, where the value of Size N may be modified accordingto the implementation.

Furthermore, although this disclosure is directed to an embodiment thatimplements the Fast Fourier Transform and the Inverse Fast FourierTransform, this is by way of illustration only and should not beconstrued to limit the scope of the disclosure. It will be appreciatedthat in an alternate embodiment of the disclosure, the Fast FourierTransform functions and the Inverse Fast Fourier Transform functions mayeasily be replaced by Discrete Fourier Transform (DFT) functions andInverse Discrete Fourier Transform (IDFT) functions, respectively. Itwill be appreciated that for DFT and IDFT functions, the value of the Nvariable may be any integer number (i.e., 1, 2, 3, 4, etc.), while forFFT and IFFT functions, the value of the N variable may be any integernumber that is a power of two (i.e., 1, 2, 4, 8, 16, etc.).

In transmit path circuitry 200, channel coding and modulation block 205receives a set of information bits, applies coding (e.g., Turbo coding),and modulates (e.g., Quadrature Phase Shift Keying (QPSK) or QuadratureAmplitude Modulation (QAM)) the input bits to produce a sequence offrequency-domain modulation symbols. Serial-to-parallel block 210converts (i.e., de-multiplexes) the serial modulated symbols to paralleldata to produce N parallel symbol streams where N is the IFFT/FFT sizeused in BS 102 and UE 116. Size N IFFT block 215 then performs an IFFToperation on the N parallel symbol streams to produce time-domain outputsignals. Parallel-to-serial block 220 converts (i.e., multiplexes) theparallel time-domain output symbols from Size N IFFT block 215 toproduce a serial time-domain signal. Add cyclic prefix block 225 theninserts a cyclic prefix to the time-domain signal. Finally, up-converter230 modulates (i.e., up-converts) the output of add cyclic prefix block225 to RF frequency for transmission via a wireless channel. The signalmay also be filtered at baseband before conversion to RF frequency.

The transmitted RF signal arrives at UE 116 after passing through thewireless channel, and reverse operations to those at BS 102 areperformed. Down-converter 255 down-converts the received signal tobaseband frequency, and remove cyclic prefix block 260 removes thecyclic prefix to produce the serial time-domain baseband signal.Serial-to-parallel block 265 converts the time-domain baseband signal toparallel time-domain signals. Size N FFT block 270 then performs an FFTalgorithm to produce N parallel frequency-domain signals.Parallel-to-serial block 275 converts the parallel frequency-domainsignals to a sequence of modulated data symbols. Channel decoding anddemodulation block 280 demodulates and then decodes the modulatedsymbols to recover the original input data stream.

Each of base stations 101-103 may implement a transmit path that isanalogous to transmitting in the downlink to user equipment 111-116 andmay implement a receive path that is analogous to receiving in theuplink from user equipment 111-116. Similarly, each one of userequipment 111-116 may implement a transmit path corresponding to thearchitecture for transmitting in the uplink to base stations 101-103 andmay implement a receive path corresponding to the architecture forreceiving in the downlink from base stations 101-103.

FIG. 4 illustrates a block diagram of a transmitter 405 and a receiver410 in a wireless communication system that may be used to implementvarious embodiments of the present disclosure. In this illustrativeexample, the transmitter 405 and the receiver 410 are devices at acommunication point in a wireless communications system, such as, forexample, wireless system 100 in FIG. 1. In some embodiments, thetransmitter 405 or the receiver 410 may be a network entity, such as abase station, e.g., an evolved node B (eNB), a remote-radio head, arelay station, an underlay base station; gateway (GW); or base stationcontroller (BSC). In other embodiments, the transmitter 405 or thereceiver 410 may be a UE (e.g., mobile station, subscriber station,etc.). In one example, the transmitter 405 or the receiver 410 is anexample of one embodiment of the UE 116 in FIG. 1. In another example,the transmitter 405 or the receiver 410 is an example of one embodimentof the base station 102 in FIG. 1.

The transmitter 405 comprises antenna(s) 415, phase shifters 420, TXprocessing circuitry 425, and controller 430. The transmitter 405receives analog or digital signals from outgoing baseband data.Transmitter 405 encodes, multiplexes, and/or digitizes the outgoingbaseband data to produce a processed RF signal that is sent and/ortransmitted via transmitter 405. For example, the TX processingcircuitry 425 may implement a transmit path that is analogous to thetransmit processing circuitry 200 in FIG. 2. Transmitter 405 may alsoperform spatial multiplexing via layer mapping to different antennas inantenna(s) 415 to transmit signals in multiple different beams. Thecontroller 430 controls the overall operation of transmitter 405. In onesuch operation, controller 430 controls the transmission of signals bythe transmitter 405 in accordance with well-known principles.

Receiver 410 receives from antenna(s) 435 an incoming RF signal orsignals transmitted by one or more transmission points, such as basestations, relay stations, remote radio heads, UEs, etc. Receiver 410includes RX processing circuitry 445 that processes the receivedsignal(s) to identify the information transmitted by the transmissionpoint(s). For example, the RX processing circuitry 445 may down-convertthe incoming RF signal(s) to produce an intermediate frequency (IF) or abaseband signal by channel estimating, demodulating, stream separating,filtering, decoding, and/or digitizing the received signal(s). Forexample, the RX processing circuitry 445 may implement a receive paththat is analogous to the receive processing circuitry 300 in FIG. 3. Thecontroller 450 controls the overall operation of the receiver 410. Inone such operation, the controller 450 controls the reception of signalsby the receiver 410 in accordance with well-known principles.

In various embodiments, the transmitter 405 is located within a TP, andthe receiver is located within a UE in a CoMP communication system. Forexample, in the CoMP communication, multiple TPs may includetransmitters similar to the transmitter 405 that transmits to the UE.The multiple TPs may be any combination of base stations (e.g., eNB,macro base stations, etc.), RHHs, and/or underlay base stations (e.g.,micro base stations, relay stations, etc.).

The illustration of transmitter 405 and receiver 410 illustrated in FIG.4 is for the purposes of illustrating one embodiment in whichembodiments of the present disclosure may be implemented. Otherembodiments of the transmitter 405 and the receiver 410 could be usedwithout departing from the scope of this disclosure. For example, thetransmitter 405 may be located in a communication node (e.g., BS, UE,RS, and RRH) that also includes a receiver, such as receiver 410.Similarly, the receiver 410 may be located in a communication node(e.g., BS, UE, RS, and RRH) that also includes a transmitter, such astransmitter 405. Antennas in the TX and RX antenna arrays in thiscommunication node may overlap or be the same antenna arrays used fortransmission and reception via one or more antenna switching mechanisms.

FIG. 5 illustrates a block diagram of a CoMP communication system 500 inaccordance with various embodiments of the present disclosure. In thisillustrative example, the CoMP communication system 500 includes a UE505 and two TPs 510 and 515. For example, the UE 505 may include areceiver and transmitter as illustrated in FIG. 4. The TPs 510 and 515may also include a receiver and transmitter as illustrated in FIG. 4.The TPs 510 and 515 may be any combination of base stations (e.g., eNB,macro base stations, etc.), RRHs, and/or underlay base stations (e.g.,micro base stations, relay stations, etc.). Additionally, TPs and UEsmay be present in the CoMP communication system 500. For example, morethan two TPs may communicate with the same UE 505.

As illustrated in FIG. 5, the UE 505 may be located anywhere between oraround the TPs 510 and 515. In order to properly perform timing and/orfrequency synchronization and/or channel estimation with the TPs 510 and515, the UE 505 may need to identify properties of the TPs 510 and 515.For example, the UE 505 may need to identify the large scale propertiesof reference symbol ports associated with the TPs 510 and 515. To assistin identifying these properties, the UE 505 may consider certain antennaports to be ‘quasi co-located’. For example, the ‘quasi co-located’antenna ports may in-fact be co-located (i.e., transmitted from the sameTP, antenna array, or antenna) or ‘quasi co-located’ antenna ports maybe located in different TPs (e.g., TPs that may have similar channelproperties). Either way, from the perspective of the UE 505, the concernis whether the UE can derive the large scale properties of one port fromthe large scale properties of another port. In other words, the UE 505may not care whether the ports are actually physically co-located, justthat the properties of the ports are similar enough to use for channelestimation, timing synchronization, and/or frequency synchronization.According to 3GPP TS 36.211 (sec 6.2.1), which is expressly incorporatedby reference herein, two antenna ports are said to be quasi co-locatedif the large-scale properties of the channel over which a symbol on oneantenna port is conveyed can be inferred from the channel over which asymbol on the other antenna port is conveyed.

Various embodiments provide methods to enable a network entity to informthe UE of a pair of DM-RS and CSI-RS ports that may be considered quasico-located by the UE, so that the UE can derive the large scale channelproperties for channel estimation for the CSI-RS port based on the DM-RSport. The network entity may inform the UE via implicit signaling. Forexample, a DM-RS port may be considered quasi co-located with a CSI-RSport if certain predefined conditions known by the UE (and the eNB) aresatisfied, (e.g., by checking existing parameter values related to DM-RSand CSI-RS). In other embodiments, the network entity may inform the UEvia explicit signaling. For example, the network entity may explicitlyconfigure the CSI-RS port/resource that can be considered quasico-located with a DM-RS port. In other embodiments, the network entitymay inform the UE via mixed implicit and explicit signaling (e.g.,implicit signaling can be complemented by explicit signaling).

In one example of implicit signaling, a DM-RS port may be assumed by theUE to be quasi co-located with a CSI-RS resource if the followingconditions are satisfied. The parameter X_(DMRS) used in sequenceinitialization to derive the DM-RS sequence (e.g., in equation 3 below)and the parameter X_(CSIRS) (configured for a CSI-RS resource) used insequence initialization to derive the CSI-RS sequence (e.g., in equation4 below) are configured to the same value. In addition, the parametern_(s) ^(DMRS) and the parameter n_(s) ^(CSIRS) are also configuredand/or determined to be the same value.

One example of an equation for calculating the DM-RS sequenceinitialization equation is provided in equation 3 below:c _(init)=(└n _(s) ^(DMRS)/2┘+1)·(2·X _(DMRS)+1)·2¹⁶ +n _(SCID)  (3)

One example of an equation for calculating the CSI-RS sequenceinitialization equation is provided in equation 4 below:c _(init)2¹⁰·(7·(n _(s) ^(CSIRS)+1)+l+1)·(2·X _(CSIRS)+1)+2·X _(CSIRS)+N _(CP)  (4)

Additionally, to assist the UE channel estimation or time/frequencysynchronization, the network entity may configure the X parameters forDM-RS and CSI-RS transmissions (i.e., X_(DMRS), X_(CSIRS)) from a TP tobe the same value and, similarly, the n_(s) parameters for DM-RS andCSI-RS transmissions (n_(s) ^(DMRS), n_(s) ^(CSIRS)) from a TP to be thesame value.

FIG. 6 illustrates a DM-RS and CSI-RS parameter configuration in a CoMPcommunication system 600 according to various embodiments of the presentdisclosure. In this illustrative embodiment, n_(s) is assumed to becommon for all TPs under the coverage of macro TP 610. This example isapplicable for the CoMP scenarios 3 and 4.

As illustrated, the UE 605 can be RRC configured with two X values {X1,X2} for DMRS scrambling. Assuming DPS type CoMP transmission, dependingon the dynamically chosen X value in the downlink grant, the UE 605 canderive the corresponding CSI-RS resource with the same X value as quasico-located with the DMRS and thus, shares the same large scaleproperties. If more than one CSI-RS resource configured for the UE havethe same X_(CSIRS) values, the multiple CSI-RS resources with the sameX_(CSIRS) values may correspond to multiple sets of CSI-RS ports thatare not quasi co-located. As a result, the conditions stated above maynot be sufficient. When the UE 605 is scheduled, a PDSCH and a DM-RSport(s) with the same X_(DMRS) value as the X_(CSIRS) shared by multipleCSI-RS resources, there is an ambiguity on which a CSI-RS resource theUE 605 may assume the quasi co-location to hold. To resolve this issue,the UE 605 can be signaled (e.g., in the PDCCH or EPDCCH that schedulesthe PDSCH) which CSI-RS resource is quasi co-located with the DM-RScorresponding to the scheduled PDSCH as illustrated, for example, inTABLE 2 below. This is an example of mixed implicit and explicitsignaling. The signaling bits in the DCI format may be present only ifthere are multiple CSI-RS resources with the same X_(CSIRS) value thatcannot be assumed quasi co-located. In one embodiment, the UE 605 mayassume the signaling exists if the UE 605 determines that there aremultiple CSI-RS resources with the same X_(CSIRS) value. In anotherembodiment, the UE 605 only assumes the signaling exists if a higherlayer signaling indicates as such. In yet another embodiment, thesignaling is assumed to exist whenever there are multiple CSI-RSresources configured.

The number of bits in the DCI format can be log₂(N), where N is thenumber of CSI-RS resources configured to the UE (CoMP measurement setsize), the maximum number of CSI-RS resources that can be configured tothe UE (maximum CoMP measurement set size), or fixed to a value (e.g., 1or 2). If the number of CSI-RS resources configured to the UE 605 ismore than the fixed value, higher layer signaling (e.g., RRC) can beused to indicate which subset of the CSI-RS resources configured shallbe addressed by the signaling bits in the DCI format. TABLE 2illustrates example signaling to indicate the quasi co-located CSI-RSresource with the assigned DM-RS (i.e., 1 bit signaling to switchbetween two CSI-RS resources).

TABLE 2 CSI-RS resource considered quasi co-located DCI field value withthe assigned DM-RS in the DCI 0 CSI-RS resource 1 1 CSI-RS resource 2

In another example, a single CSI-RS resource may correspond to multiplegroups of ports, where each group is quasi-co-located, while theindividual groups are not quasi co-located. The network entity mayconfigure the CSI-RS resources this way to support transparent jointtransmission with a single CSI-RS resource. In this example, thesignaling described above may also include information of a port index(or a port group or port pair) in addition to a CSI-RS resource, forexample, as illustrated in TABLE 3. In another example, the UE mayassume that quasi co-location association only applies to a fixed port,(e.g., the first port of the corresponding CSI-RS resource (or the firstand the second port)). In another example, whether the relation appliesto a fixed port index or the whole set may be configurable by thenetwork entity, for example, based on whether transparent JT CoMP issupported. TABLE 3 illustrates example signaling to indicate the quasico-located CSI-RS resource and port with the assigned DM-RS (e.g., twobit signaling to switch between four combinations of CSI-RS resourcesand ports).

TABLE 3 CSI-RS resource considered quasi co-located DCI field value withthe assigned DM-RS in the DCI 00 CSI-RS resource 1, CSI-RS port x1 01CSI-RS resource 1, CSI-RS port x2 10 CSI-RS resource 2, CSI-RS port y111 CSI-RS resource 2, CSI-RS port y2

In various embodiments, the UE may first be configured with a set ofX_(DMRS) and CSI-RS resources. The UE then determines which DM-RS portwith a X_(DMRS) value and CSI-RS resource is to be assumed quasico-located as described above. Upon receiving PDCCH or EPDCCH, the UEchecks the assigned X_(DMRS) value and any additional signaling (ifpresent) that indicates a single CSI-RS resource (and port or ports whenthere are multiple CSI-RS resources with the matching X_(CSIRS) value)and determines the quasi co-location relationship(s).

Embodiments of the present disclosure recognize that explicit signalingto complement the implicit X_(DMRS) and X_(CSIRS) condition checking mayincur additional dynamic signaling overhead. To avoid or reduce theamount of dynamic signaling overhead needed, various embodiments of thepresent disclosure define, among the set of CSI-RS resources with thesame X_(CSIRS) value, the quasi co-location relationship between aCSI-RS resource (and port(s)) and a DM-RS port index. For example, thefirst CSI-RS resource (and the port(s) x(s)) are assumed quasico-located with DM-RS port 7 (which has the same X_(DMRS) value as theX_(CSIRS) value), and the second CSI-RS resource (and the port(s) y(s))are assumed quasi co-located with DM-RS port 8 (which has the sameX_(DMRS) value as the X_(CSIRS) value), etc. as illustrated, forexample, in TABLE 4 below. In another example, higher signaling mayexplicitly indicate which DM-RS port index/indices may be assumed to bequasi co-located with a CSI-RS resource (and port(s)) or vice versa, andthis signaling can be provided along with a CSI-RS configuration RRCmessage. For example, if both port 7 and port 8 are assigned to the UEin the same subframe, the default quasi co-located CSI-RS resource (andport(s)) can be defined (e.g. the first CSI-RS resource (and the firstport)). TABLE 4 illustrates an example of quasi co-location associationbetween DM-RS port index and CSI-RS resource (and port).

TABLE 4 DM-RS port index CSI-RS resource (and port) considered (assignedin DCI) quasi co-located with the DM-RS port 7 CSI-RS resource 1 (andport x) 8 CSI-RS resource 2 (and port y)

In various embodiments, the UE is configured with the set of X_(DMRS)and CSI-RS resources. The UE then determines which DM-RS port with aX_(DMRS) value and CSI-RS resource is to be assumed quasi co-located asdescribed above. Upon receiving PDCCH/EPDCCH, the UE checks the assignedX_(DMRS) value and the DM-RS port index determine the quasi co-locationrelationship (e.g., as illustrated in TABLE 4).

If CoMP JT is supported and/or configured and a single CSI-RS resourcemay consist of CSI-RS ports that cannot be assumed to be quasico-located, the X parameters condition checking may not be sufficient.In this example, there may be only one CSI-RS resource configured. Thisissue may be resolved by additionally defining that a DM-RS port withindex j may be assumed to be quasi co-located with the CSI-RS port indexj+8 (assuming that the port indexing of a CSI-RS resource starts fromport 15) as illustrated, for example, in TABLE 5. For example, if a UEis configured with 2 CSI-RS ports (e.g., ports 15 and 16), and if the UEis assigned DM-RS port 7 for PDSCH demodulation, the UE can derive thelarge scale channel properties required for the DMRS port 7 channelestimation from measuring CSI-RS port 15, but the UE cannot use CSI-RSport 16 for the same purpose. Whether or not the UE should apply thisassumption can be signaled/configured by the network. In someembodiments, this additional definition may be used in a stand-alonemanner, i.e. independently of other quasi co-location indicationtechniques. TABLE 5 illustrates an example quasi co-location associationbetween DM-RS port index and CSI-RS port.

TABLE 5 DM-RS port index CSI-RS port considered quasi co- (assigned inDCI) located with the DM-RS port 7 CSI-RS port 15 8 CSI-RS port 16

The quasi co-location relationship between the DM-RS and the CSI-RS canbe given by explicit RRC signaling from the network (i.e., no conditionbetween X_(DMRS) and X_(CSIRS) is necessary). In one embodiment, thisexplicit signaling includes that for each DM-RS resource configured forthe UE, there is also a CSI-RS resource (and port(s) within a resource),indicated by the network entity, where the UE may assume quasico-location to hold for the corresponding DM-RS ports and CSI-RS ports.In one example of explicit signaling, the network entity may configurethe UE with a set of X_(DMRS) values (e.g., X_(DMRS)(0) and X_(DMRS)(1))and a set of CSI-RS resources (i.e., M sets of CSI-RS resources). Foreach X_(DMRS) configured, there may be log₂(M) bits to indicate whichCSI-RS resource the UE may assume quasi co-location to hold, forexample, as illustrated in TABLE 6 below. In another example, a bitmapof M bits can be configured for each X_(DMRS) configured. One advantageof the bitmap approach is that more than one CSI-RS resource can beindicated to be quasi co-located with the DM-RS. The signaling may alsoinclude the port indices within each CSI-RS resource, and additionalsignaling bits may be needed. To provide further flexibility of quasico-location association for the network entity, the DM-RS port index forthe same DM-RS resource may also be indicated, for example, asillustrated in TABLE 7 below. If the quasi co-location association(e.g., as illustrated in TABLE 6 or TABLE 7) is configured (e.g., byRRC), the DCI signaling of X_(DMRS) and port index indicates the quasico-located CSI-RS resource (and port).

TABLE 6 illustrates an example of explicit signaling for quasico-location association between DM-RS resources and CSI-RS resources(and ports). CSI-RS resources 1 and 2 may or may not be the same CSI-RSresource. Similarly, ports x and y may or may not be the same portindex.

TABLE 6 CSI-RS resource (and port) considered DM-RS Resource quasico-located with the DM-RS resource X_(DMRS)(0) CSI-RS resource 1 (andport x) X_(DMRS)(1) CSI-RS resource 2 (and port y)

TABLE 7 illustrates an example of explicit signaling for quasico-location association between DM-RS resources and CSI-RS resources(and ports). Any pair of CSI-RS resource 1, 2, 3, 4 may be the same ordifferent CSI-RS resource. Similarly, any pair of port x1, . . . , x4may be the same or different port index.

TABLE 7 DM-RS Resource CSI-RS resource (and port) considered quasi andport co-located with the DM-RS resource and port X_(DMRS)(0) and port 7CSI-RS resource 1 (and port x1) X_(DMRS)(0) and port 8 CSI-RS resource 2(and port x2) X_(DMRS)(1) and port 7 CSI-RS resource 3 (and port x3)X_(DMRS)(1) and port 8 CSI-RS resource 4 (and port x4)

If more than one DM-RS port can be further assumed quasi co-located(e.g., by predefining the quasi co-location relationship in thespecification or by network signaling as discussed in greater detailbelow), the UE may be able to use more CSI-RS ports (which aredetermined according to aforementioned conditions) to improve theestimation by the UE of the large scale channel properties by averagingover the measurements from the CSI-RS ports. In one embodiment, thenetwork entity may have an option to signal a choice between one of thedescribed associations for quasi co-location or assume that a DMRS portcannot be assumed co-located with any CSI-RS port.

Various embodiments provide methods to enable the network to inform theUE which pair of DM-RS and CRS ports may be considered quasi co-locatedby the UE such that the UE can derive the large-scale channel propertiesrequired for channel estimation for the CRS port based on the DM-RSport. The network entity may inform the UE via implicit signaling. Forexample, a DM-RS port may be considered quasi co-located with a CRS portif certain predefined conditions known by the UE (and the eNB) aresatisfied, (e.g., by checking of existing parameter values related toDM-RS and CRS). In other embodiments, the network entity may inform theUE via explicit signaling. For example, the network entity mayexplicitly configure the CRS port/resource that can be considered quasico-located with a DM-RS port. In other embodiments, the network entitymay inform the UE via mixed implicit and explicit signaling (e.g.,implicit signaling can be complemented by explicit signaling).

In one example of implicit signaling, a DM-RS port may be assumed by theUE to be quasi co-located with a CRS resource if the followingconditions are satisfied. The parameter X_(DMRS) used in sequenceinitialization to derive the DM-RS sequence (e.g., in equation 5 below)and the parameter N_(ID) ^(cell) used in sequence initialization toderive the CRS sequence (e.g., in equation 6 below) are the same value.In addition, the parameter n_(s) ^(DMRS) and the parameter n_(s) ^(CRS)are also configured and/or determined to be the same value.

One example of an equation for calculating the DM-RS sequenceinitialization equation is provided in equation 5 below:c _(init)=(└n _(s) ^(DMRS)/2┘+1)·(2·X _(DMRS)+1)·2¹⁶ +n _(SCID)  (5)

One example of an equation for calculating the CRS sequenceinitialization equation is provided in equation 6 below:c _(init)2¹⁰·(7·(n _(s) ^(CRS)+1)+l+1)·(2·N _(ID) ^(cell)+1)+2·N _(ID)^(cell) +N _(CP)  (6)

The scrambling sequence itself can be generated according to 3GPP TS36.211 § 6.10.1.1, which is expressly incorporated by reference herein.The N_(ID) ^(cell) for the CRS port can correspond to the serving cellor can correspond to one of the detected or reported neighboring cells(e.g., where the RSRP/RSRQ report of the neighboring cell was sent). IfN_(ID) ^(cell) corresponds to one of the neighboring cells, this impliesDL CoMP operation (i.e., the UE is actually receiving DM-RS and PDSCHfrom the neighboring cell instead of the serving cell). If the parameterX_(DMRS) of DM-RS port does not match any known neighboring cells'N_(ID) ^(cell), the UE may assume that the corresponding DM-RS port isquasi co-located with the CRS port of the serving cell. In oneembodiment, the UE may only assume a DM-RS port is quasi co-located withthe CRS port of the serving cell if the parameter X_(DMRS) of the DM-RSport matches with the serving cell's N_(ID) ^(cell).

If there is more than one CRS port available for a serving cell or aneighboring cell with the same N_(ID) ^(cell) and n_(s) ^(CRS) if theCRS ports cannot be assumed to be quasi co-located by the UE, thenetwork entity can additionally signal which CRS port is to be assumedto be quasi co-located with a DM-RS port (e.g., port 0, port 1, port 2,port 3, a subset of CRS ports, or all CRS ports). The signaling can bedone in a semi-static manner (e.g., via MAC or RRC signaling) or in adynamic manner (e.g., signaling in PDCCH). The default can be CRS port0, all CRS ports, or provided by higher layer signaling if dynamicsignaling in PDCCH is used to indicate a value that may be differentfrom the default value. This is an example of mixed implicit andexplicit signaling. In another example, the quasi co-location assumptionof DM-RS ports and CRS ports can be predefined (e.g., as illustrated inTABLE 8 below). One advantage of a predefined rule is saving ofsignaling overhead. TABLE 8 illustrates rules for quasi co-locatedports.

TABLE 8 Quasi co-located set CRS ports indices DM RS ports indices Set 1(0) or (0, 3) EX1: (7) EX2: (7, 8) EX3: (7, 8, 11, 13) Set 2 (1) or (1,2) EX1: (8) EX2: (9, 10) EX3: (9, 10, 12, 14)

To provide additional flexibility for the network entity, the quasico-location assumption according to the methods described above may onlybe valid if indicated by the network entity (i.e. it may also bepossible for the network entity to indicate that the quasi co-locationof the CRS port and the DM-RS port cannot be assumed by the UE).

The quasi co-location relationship between the DM-RS and the CRS can begiven by explicit signaling from the network entity. One method ofexplicit signaling includes that for each DM-RS resource configured forthe UE, there is also a CRS resource and/or port(s) within a resource,indicated by the network, where the UE may assume quasi co-location tohold for the corresponding DM-RS ports and CRS ports. A CRS resource canbe given by a configuration of an n_(s) ^(CRS).

Allowing the UE to assume quasi co-location of a DM-RS port with a CRSport may be beneficial to improve time and/or frequency synchronizationor to improve the channel estimation performance for the DM-RS port inorder to improve the PDSCH demodulation performance. These embodimentsalso extend to quasi co-location relationship of DM-RS and tracking RS(TRS) that may exist in a non-backward compatible carrier (i.e., a newcarrier type) to facilitate time/frequency synchronization. In theseembodiments, there may only be one TRS port.

Various embodiments provide methods to enable a network entity to informthe UE of a pair of CSI-RS and CRS ports may be considered quasico-located by the UE, so that the UE can derive the large scale channelproperties required for channel estimation or time/frequencysynchronization for the CSI-RS port based on the CRS port. The networkentity may inform the UE via implicit signaling. For example, a CSI-RSresource and/or port may be considered quasi co-located with a CRS portif certain predefined conditions known by the UE (and the eNB) aresatisfied, (e.g., by checking of existing parameter values related toCRS and CSI-RS). In other embodiments, the network entity may inform theUE via explicit signaling. For example, the network entity mayexplicitly configure the CRS port and/or resource that can be consideredquasi co-located with a CSI-RS port and/or resource. In otherembodiments, the network entity may inform the UE via mixed implicit andexplicit signaling (e.g., implicit signaling can be complemented byexplicit signaling).

In one example of implicit signaling, a CSI-RS resource and/or port canbe assumed by the UE to be quasi co-located with a CRS port if thefollowing conditions (hereinafter “Conditions A”) are satisfied.

The parameter X_(CSIRS) used in sequence initialization to derive theCSI-RS sequence (e.g., in equation 7 below) and the parameter N_(ID)^(cell) used in sequence initialization to derive the CRS sequence arethe same value. In addition, the parameter n_(s) ^(CSIRS) and theparameter n_(s) ^(CRS) are also configured and/or determined to be thesame value.

One example of an equation for calculating the CSI-RS sequenceinitialization equation is provided in equation 7 below:c _(init)2¹⁰·(7·(n _(s) ^(CSIRS)+1)+l+1)·(2·X _(CSIRS)+1)+2·X _(CSIRS)+N _(CP)  (7)

One example of an equation for calculating the CRS sequenceinitialization equation is provided in equation 8 below:c _(init)2¹⁰·(7·(n _(s) ^(CRS)+1)+l+1)·(2·N _(ID) ^(cell)+1)+2·N _(ID)^(cell) +N _(CP)  (8)

The N_(ID) ^(cell) for the CRS port can correspond to the serving cellor can correspond to one of the detected neighboring cells/reportedneighboring cells (e.g., where the RSRP/RSRQ report of the neighboringcell was sent). If N_(ID) ^(cell) corresponds to one of the neighboringcells, it implies DL CoMP operation (i.e., the UE is actually receivingCSI-RS from the neighboring cell instead of the serving cell). If theparameter X_(CSIRS) of CSI-RS resource and/or port does not match anyknown neighboring cells' N_(ID) ^(cell), the UE may assume that thecorresponding CSI-RS resource and/or port is quasi co-located with theCRS port of the serving cell. In one embodiment, the UE may only assumea CSI-RS resource and/or port is quasi co-located with the CRS port ofthe serving cell if the parameter X_(CSI-RS) of CSI-RS resource and/orport matches the serving cell's N_(ID) ^(cell). In some embodiments, thelarge scale properties referred to may be limited to the received timingonly as the CSI-RS density may not be enough for the UE to acquireaccurate timing information. In other embodiments, the large scaleproperties referred to may additionally or alternatively include delayspread, Doppler spread, and frequency shift.

If there are more than one CRS ports with the same N_(ID) ^(cell) andn_(s) ^(CRS), and if the CRS ports cannot be assumed to be quasico-located by the UE, the network entity can signal which CRS port is tobe assumed to be quasi co-located with each CSI-RS resource and/or port(e.g., port 0, port 1, port 2, port 3, a subset of ports, or all CRSports). The signaling can be done in a semi-static manner (e.g. MAC orRRC signaling). This is an example of a mixed implicit and explicitsignaling method.

To provide additional flexibility for the network entity, the quasico-location assumption as described above (i.e., in Conditions A) mayonly be valid if indicated by the network entity, (i.e., it is possiblefor the network entity to indicate that the quasi co-location of the CRSport and the CSI-RS port cannot be assumed by the UE). In one example,the quasi co-location assumption according to Conditions A is thedefault UE behavior unless higher-layer signaling is provided for aCSI-RS resource to indicate if quasi co-location with a CRS (complyingwith a certain condition) may not be assumed. Separate higher-layersignaling may be provided for separate CSI-RS resources for flexibleconfiguration.

In another example, non-quasi co-location is the default UE assumption.Quasi co-location with a CRS (complying with a certain condition) mayonly be assumed if higher-layer signaling is provided for a CSI-RSresource. Separate higher-layer signaling can be provided for separateCSI-RS resources for flexible configuration. In another example,separate higher-layer signaling indications for different large scalechannel properties are provided. For example, one higher-layer signalingindication is provided for the received timing and another is providedfor the delay spread, Doppler spread, and frequency shift. Theseseparate signaling indications are beneficial for the CoMP scenario 4 asa CSI-RS and a CRS may only share the same received timing, but not theother large-scale properties.

Based on the embodiments described above, one example design for release11 UE behavior may include that a CSI-RS resource may be assumed quasico-located with a CRS resource with respect to received timing if thevirtual cell ID of the CSI-RS matches with cell ID of the CRS (e.g.,cell IDs can correspond to that of the serving cell or one of thedetected neighboring cells/reported neighboring cells (e.g., where theRSRP/RSRQ report of the neighboring cell was sent)). If no match isfound, UE may only assume quasi co-location in terms of received timingwith the CRS port of the serving cell. When the virtual cell ID of theCSI-RS and the cell ID of the CRS of a cell match (e.g., cell IDs cancorrespond to that of the serving cell or one of the detectedneighboring cells/reported neighboring cells (e.g., where the RSRP/RSRQreport of the neighboring cell was sent)), quasi co-location assumptionbetween the CSI-RS and the CRS with respect to certain properties (e.g.,delay spread, frequency shift, Doppler spread) may also be assumed bythe UE. This assumption can be the default UE assumption, unlesshigher-layer signaling indicates that the CSI-RS resource is not quasico-located with the CRS with respect to the certain properties (e.g.,delay spread, frequency shift, Doppler spread).

This example design may address the needs for CoMP scenarios 1, 2, 3,and 4 as described in 3GPP TS 36.819. For CoMP scenarios 1, 2, and 3,the virtual cell ID of the CSI-RS is normally the same as the cell ID.This may also be needed for supporting legacy UEs (e.g., release 10UEs). For CoMP scenario 4, the virtual cell IDs of the TPs can either bethe same as the serving cell in case the CSI-RSs are orthogonal in timeand/or frequency, or the virtual cell IDs can be different forinterference randomization purposes in case the TPs' CSI-RS REs overlap.In either case, for CoMP scenario 4, the UE may assume that the receivedtiming for the CSI-RS is to be the same as the CRS of the serving cell.However, the quasi co-location assumption of delay spread and Dopplerspread may not generally be assumed for CoMP scenario 4, since CRS maybe transmitted in a system frame number (SFN) manner while CSI-RS can betransmitted only from a TP. Nevertheless, for CoMP scenarios 1, 2, and3, as well as scenarios without CoMP, the quasi co-location assumptionof the CSI-RS ports and the CRS ports will typically work. Thedemodulation performance may be unnecessarily degraded if the UE is notallowed to take advantage of the quasi co-location assumption. A commondenominator for the aforementioned scenarios is that the virtual cell IDof the CSI-RS is normally the same as the cell ID (as assumed by legacyUEs as well), which can serve as the condition for the quasi co-locationassumption. However, for CoMP scenario 4, such condition alone may notbe sufficient, as multiple TPs may be configured with the same virtualcell id. Therefore, additional higher-layer signaling is provided foreach CSI-RS resource to indicate if quasi co-location assumption withthe CRS is not allowed.

The example design can also provide benefits of quasi co-locationassumptions for a legacy UE (e.g., a release 10 UE). For example, aCSI-RS resource may be assumed quasi co-located with a CRS resource withrespect to received timing, delay spread, frequency shift, and/orDoppler spread by legacy UEs. This assumption is valid for legacy UEsoperating in a network that deploys CoMP scenario 1, 2, and 3. Theassumption is also valid for a network that deploys CoMP scenario 4 aslong as the CSI-RS and the CRS are transmitted from the same set oftransmission points (e.g., SFN transmission).

Based on the embodiments described above, another example design forrelease 11 UE behavior may include that for each CSI-RS resource, thenetwork entity indicates by higher-layer signaling (e.g., higher-layersignaling A) that CSI-RS ports and CRS ports may be assumed as quasico-located with respect to one or more of the large-scale properties. Ifthe higher layer signaling A indicates that CSI-RS ports and CRS portsmay be assumed as quasi co-located with respect to one or more of thelarge-scale properties, the UE may assume quasi co-location with respectto one or more of the large-scale properties between all the CSI-RSports of the CSI-RS resource and CRS ports, where the cell ID of the CRSports (which can be the serving cell or the neighboring cells detectedor reported by the UE) matches with the virtual cell ID of the CSI-RSresource. In the absence of network signaling (higher-layer signalingA), CSI-RS ports and CRS ports shall not be assumed as quasi co-locatedwith respect to all properties.

The UE behavior described in the above example designs may beconditioned on whether release 11 CSI-RS resource(s) are configured. Inother words, the quasi co-location assumptions above may only beapplicable if release 11 CSI-RS resources information element (IE) ofASN.1 is configured. If the UE is configured with a legacy CSI-RSresource IE, then the UE behavior follows the legacy behavior. Inanother example, the UE behavior described in the above example designsmay be conditioned on the transmission mode configured. Specifically,the quasi co-location assumptions above may only be applicable iftransmission mode 10 is configured. If the UE is configured withtransmission mode 9, then the UE behavior may follow the legacybehavior.

The quasi co-location relationship between the CSI-RS and the CRS may begiven by explicit signaling from the network entity. One method ofexplicit signaling includes that for each CSI-RS resource and/or portconfigured for the UE, there is also a CRS resource and/or port(s)within a resource, indicated by the network, where the UE may assumequasi co-location to hold for the corresponding CSI-RS ports and CRSports. A CRS resource can be given by a configuration of N_(ID) ^(cell)and n_(s) ^(CRS). N_(ID) ^(cell) determines the initialization of theCRS scrambling sequence and the frequency shift of the CRS resourceelements according to 3GPP TS 36.211 § 6.10.1.1 and § 6.10.1.2, whichare expressly incorporated by reference herein. Allowing the UE toassume quasi co-location of a CSI-RS resource and/or port with a CRSport is beneficial to improve the channel estimation and/ortime/frequency synchronization performance for the CSI-RS resourceand/or port, in order to improve the CSI feedback accuracy. Thisembodiment also extends to quasi co-location relationship of CSI-RS andtracking RS (TRS) that may exist in a non-backward compatible carrier(e.g., a new carrier type). In this case, there may be only one TRSport.

Based on the embodiments of the present disclosure described above, oneexample design for Rel-11 UE behavior may include that for each CSI-RSresource, the network entity indicates by higher layer signaling (e.g.,higher-layer signaling A) that CSI-RS ports and CRS ports may be assumedas quasi co-located with respect to one or more of the large-scaleproperties. In one embodiment, if the higher-layer signaling A indicatesthat CSI-RS ports and CRS ports may be assumed as quasi co-located withrespect to one or more of the large-scale properties, the UE may assumequasi co-location with respect to one or more of the large-scaleproperties between all the CSI-RS ports of the CSI-RS resource and CRSports associated with the serving cell ID. In another embodiment, if thequasi co-location Type B signaling indicates that CSI-RS ports and CRSports may be assumed as quasi co-located with respect to one or more ofthe large-scale properties (e.g., Doppler spread and Doppler shift), thenetwork entity also indicates a cell ID (higher layer signaling B) basedon which the UE may assume quasi co-location with respect to one or moreof the large-scale properties between all the CSI-RS ports of the CSI-RSresource and CRS ports associated with the signaled cell ID. In anotherembodiment, higher-layer signaling A and higher-layer signaling B is thesame. In other words, higher-layer signaling of the cell ID of the quasico-located CRS also indicate that the CSI-RS is quasi co-located withthe CRS associated with the cell ID. In the absence of network signaling(e.g., higher-layer signaling A), CSI-RS ports and CRS ports shall notbe assumed as quasi co-located with respect to all properties.

Based on the embodiments of the present disclosure described above,another example design for release 11 UE behavior may include that thenetwork entity indicates by higher layer signaling (e.g., higher-layersignaling C) that the CSI-RS ports of a CSI-RS resource X and the CRSports of the serving cell may be assumed as quasi co-located withrespect to one or more of the large-scale properties. The CSI-RSresource X can be fixed to that corresponding to the smallest CSI-RSresource ID of the CSI-RS resources configured (i.e., if there is onlyone CSI-RS resource configured, then CSI-RS resource X is the onlyCSI-RS resource configured). The CSI-RS resource X can be configured byhigher layer signaling (e.g., RRC) to be CSI-RS resource, which is partof the release 11 CSI-RS resources configured. The signaling canindicate the CSI-RS resource ID. In the absence of network signaling(e.g., higher-layer signaling C), CSI-RS ports and CRS ports shall notbe assumed as quasi co-located with respect to all properties.

The UE behavior described in the above example designs may beconditioned on whether release 11 CSI-RS resource(s) are configured. Inother words, the behavior above may only be applicable if release 11CSI-RS resources information element (IE) of ASN.1 is configured. If theUE is configured with a legacy (e.g., release 10) CSI-RS resource IE,then the UE behavior follows the legacy behavior. In another example,the UE behavior described in the above design examples may beconditioned on the transmission mode configured. For example, thebehavior above may only be applicable if transmission mode 10 isconfigured. If the UE is configured with transmission mode 9, then theUE behavior follows the legacy behavior.

In various embodiments of the present disclosure, if more than one DM-RSport can be assumed to be quasi co-located, it may be advantageous toassign DM-RS ports belonging to the same CDM group to be quasico-located so that the orthogonality of the DM-RS is not negativelyaffected. For example, ports 7 and 8 can be quasi co-located, and ports9 and 10 can be quasi co-located.

In one example, the possible quasi co-location relationships of DM-RSports are illustrated in TABLE 9 below. Network signaling (e.g., viaRRC) may also be used to indicate which case of relationship is to beassumed by the UE (e.g., via 2-bit signaling).

TABLE 9 No. DM RS ports Case 2 4 8 0 (7), (8) (7), (8), (9), (10) (7),(8), (9), (10), (11), (12), (13), (14) 1 (7, 8) (7, 8), (9, 10) (7, 8),(9, 10), (11, 13), (12, 14) 2 — (7, 8, 9, 10) (7, 8, 11, 13), (9, 10,12, 14) 3 — — (7, 8, 9, 10, 11, 12, 13, 14)

For case 1 above, when the number of DM-RS ports assigned is 4, the UEmay assume ports 7 and 8 are quasi co-located, whereas ports 9 and 10are quasi co-located.

The above described embodiments may be used to improve the channelestimation and/or time/frequency synchronization performance for PDSCHreception (based on DM-RS) or for CSI feedback (based on CSI-RS). Invarious embodiments, the UE may still receive the DL signals using asingle FFT timing when configured to operate in CoMP. The followingUE-specific signaling, which may be semi-static or dynamic, is proposedin order to assist the UE to determine the DL timing (i.e., FFT timing)for DL signal reception when configured to operate in CoMP, so that theSNR of DL signals reception can be enhanced. The network entity mayprovide network signaling (e.g. via RRC) to indicate if the UE maysynchronize with DL signals (e.g., RS) from a non-serving cell (e.g.,neighboring cell) or a TP (which may or may not have the same cell ID asthe serving cell) for DL reception (e.g., PDSCH demodulation, CSI-RSreception, etc.). Without the signaling, the UE may synchronize with theserving cell. Furthermore, the network can indicate a specific cell(e.g., by cell ID) or TP (CSI-RS resource (and optionally cell ID)) forsynchronization, or the UE can select from a CoMP measurement setconfigured as described in U.S. patent application Ser. No. 13/626,572.The TP may be indicated by a CSI-RS resource configuration (e.g.configuration index, subframe configuration index, number of CSI-RSports, and signaling required for sequence initialization).

In addition, signaling can be provided to indicate the type of RS thatshould be used for synchronization, e.g. CRS, CSI-RS, or both. In caseof CRS, additional signaling may be optionally provided by the networkto indicate which CRS port should be used by the UE for synchronization,e.g. port 0 or 1 and the cell ID. The default port can be port 0 of theserving cell. In case of CSI-RS, the UE may recognize a CSI-RS port asbelonging to a non-serving cell if the parameter X_(CSIRS) used insequence initialization to derive the CSI-RS sequence matches with thevalue (used in sequence initialization to derive the CRS) of a detectedneighboring cell.

One example of an equation for calculating the CSI-RS sequenceinitialization equation is provided in equation 9 below:c _(init)2¹⁰·(7·(n _(s) ^(CSIRS)+1)+l+1)·(2·X _(CSIRS)+1)+2·X _(CSIRS)+N _(CP)  (9)

One example of an equation for calculating the CRS sequenceinitialization equation is provided in equation 10 below:c _(init)2¹⁰·(7·(n _(s) ^(CRS)+1)+l+1)·(2·N _(ID) ^(cell)+1)+2·N _(ID)^(cell) +N _(CP)  (10)

Upon recognizing a CSI-RS port belonging to a neighboring cell, the UEmay use the CRS of the neighboring cell to assist with time/frequencysynchronization, provided that the quasi co-location assumption holds asdescribed above. As a result, both CRS and CSI-RS information may beused for synchronization purposes. If the quasi co-location assumptiondoes not hold, the UE may not use CRS of the neighboring cell to assistwith time/frequency synchronization.

The UE has to always be able to receive signals from the serving cellwhere the timing is given by the PSS/SSS and the serving cell's CRS.Therefore, if configured by the network entity according to thisembodiment to determine a new FFT timing for CoMP or if multiple CSI-RSresources are configured as described in U.S. patent application Ser.No. 13/626,572, the FFT timing is determined as the earliest signalarrival time of the serving cell's PSS/SSS/CRS and the new timingreference as described in this embodiment or in U.S. patent applicationSer. No. 13/626,572.

However, for the purpose of uplink transmission and timing advance, thetiming reference may need to be based on PSS/SSS/CRS. In one method, thetiming reference is also modified accordingly for the uplinktransmission and timing advance.

The above-described embodiments may be used to improve the channelestimation and/or time/frequency synchronization performance for PDSCHreception (based on DM-RS) or for CSI feedback (based on CSI-RS). Invarious embodiments, the UE may still receive the DL signals using asingle FFT timing when configured to operate in CoMP. The followingUE-specific signaling, which may be semi-static or dynamic, is proposedin order to assist the UE to determine the DL timing (i.e., FFT timing)for DL signal reception when configured to operate in CoMP so that theSNR of DL signals reception can be enhanced.

The network entity may provide network signaling (e.g. by RRC or MACsignaling) to indicate the adjustment of FFT timing that should beapplied by the UE with respect to the FFT timing acquired from theserving cell (e.g., from PSS/SSS/CRS of the serving cell). For example,if the UE's nominal FFT timing (e.g., FFT timing derived fromPSS/SSS/CRS of the serving cell) is t, the network signaling canindicate Δt, and the UE is recommended to consider the FFT timing of theUE to be t−Δt. Stricter conditions can also be applied such that the UEis required to modify the FFT timing to be t−Δt. More generally, the UEcan take into account the network signaling of Δt in receiveroperations, which could include one or more of timing estimation,channel estimation, decoding, and demodulation. For example, Δt may bedefined as a worst case timing offset.

In many examples, Δt is a positive value, so that the timing adjustmentinvolves advancing the FFT timing to recover potential earlier pathsthat may be missed by the UE as described above. However, a negative Δtvalue may be used in some embodiments. Optionally, the UE can performfurther optimization of FFT timing adjustments in addition to theindicated timing, for example, t−Δt−δt, where δt is an additionaladjustment deemed appropriate by the UE.

As discussed above, signaling can be provided by the network entity(e.g., via higher-layer signaling, such as RRC) to indicate to the UEthe quasi co-location relationship between a DM-RS resource (e.g.,identified as a set of DM-RS configurations, such as virtual cell ID andsubframe offset etc. associated with a particular n_(SCID) value) and aCSI-RS resource (e.g., identified by its resource ID or CSI process id).As one example, TABLE 10 illustrates quasi co-location associationbetween DM-RS resources and CSI-RS resources where X_(DMRS)(0) isconsidered the DMRS virtual cell ID indicated by n_(SCID)=0 andX_(DMRS)(1) is considered the DMRS virtual cell ID indicated byn_(SCID)=1.

TABLE 10 CSI-RS resource considered quasi co- DM-RS Resource locatedwith the DM-RS resource DM RS resource 1 (X_(DMRS)(0), . . .) CSI-RSresource 1 DM RS resource 2 (X_(DMRS)(1), . . .) CSI-RS resource 2

The number of DM-RS resources and the number of CSI-RS resourcesconfigured to the UE for L1 CSI feedback may be different. For example,the number of DM-RS resources configured may be 2, and the number ofCSI-resources configured for CoMP measurement set may be 3. In thisexample, in a typical deployment scenario, each CSI-RS resourcecorresponds to a transmission point (TP) in a CoMP coordination area,and the Dynamic Point Selection (DPS) transmission scheme can involveall three TPs. In this case, one DM-RS resource can be quasi co-locatedwith more than one CSI-RS resource but at different times (e.g.,subframe), as illustrated, for example, as shown in TABLE 11 below andFIG. 7. TABLE 11 illustrates quasi co-location association between 2DM-RS resources and 3 CSI-RS resources.

TABLE 11 CSI-RS resource considered quasi co- DM-RS Resource locatedwith the DM-RS resource DM RS resource 1 (X_(DMRS)(0), . . .) CSI-RSresource 1 DM RS resource 1 (X_(DMRS)(0), . . .) CSI-RS resource 2 DM RSresource 2 (X_(DMRS)(1), . . .) CSI-RS resource 3

FIG. 7 illustrates an example of DM-RS resource and CSI-RS resourcequasi co-location configuration changing over time in accordance withvarious embodiments of the present disclosure. In this illustrativeexample, a DM-RS resource 1 is quasi co-located CSI-RS resource 1 insubframe n but is quasi co-located with CSI-RS resource 2 in subframen+1, whereas DM-RS resource 2 is quasi co-located with CSI-RS resource 3in subframes n+2 to n+k. In this embodiment, an additional signalingmechanism may be required to indicate exactly which CSI-RS resource(e.g., CSI-RS resource 1 or 2) should be assumed quasi co-located withDM-RS resource 1 on a subframe basis. Additional bit(s) may beprovisioned in the DCI format used for assigning the DL assignment withDM-RS to indicate information such as described above. For example,given the higher-layer signaling conveying the information in TABLE 11,one additional bit may be introduced in the DL assignment to indicateeither CSI-RS resource 1 or 2 when DM-RS resource 1 is assigned. Thisinformation may be signaled without incurring additional signalingoverhead in the DCI format. In one example, two parameters in the DCIformat, namely the n_(SCID) used for DM-RS sequence initialization(e.g., equation 11 below where X_(DMRS) is the virtual cell ID indicatedby n_(SCID)) and the NDI of the disabled transport block may be used tojointly indicate the quasi co-location assumption. The n_(SCID) isassumed here to indicate the DM-RS resource. TABLE 12 below illustratesan example of the joint use of n_(SCID) and NDI of a disabled transportblock in the DCI format to indicate quasi co-location assumption. Inthis example, the interpretation of quasi co-location assumption is alsodependent on the rank assigned (i.e., the number of layers). The reusingNDI of the disabled transport block is just one example. Other bit(s) inthe DCI format can also be reused for this purpose if they serve nospecific purpose in certain cases or if reusing them for this purposedoes not cause negative effects to the purpose for which the bit(s) wereoriginally intended. One example of an equation for calculating theDM-RS sequence initialization equation is provided in equation 11 below:c _(init)=(└n _(s) ^(DMRS)/2┘+1)*(2·X _(DMRS)+1)*2¹⁶ +n _(SCID)  (11)

TABLE 12 CSI-RS resource that is quasi co- NDI of disabled located withthe n_(SCID) value in transport block in the DM-RS assigned by Rank theDCI format DCI format the DCI format 1 n_(SCID) = 0 0 CSI-RS resource 11 n_(SCID) = 0 1 CSI-RS resource 2 1 n_(SCID) = 1 Don't care CSI-RSresource 3 2 n_(SCID) = 0 N/A CSI-RS resource 1 2 n_(SCID) = 1 N/ACSI-RS resource 2 >2 n_(SCID) = 0 (fixed) N/A CSI-RS resource 1

The UE may be configured by higher-layer signaling (e.g., RRC) on thesemi-static quasi co-location relationship between DM-RS resources andCSI-RS resources, for example, as illustrated in TABLE 11 or describedin further detail below. The UE detects the n_(SCID) value in the DCIformat to determine the quasi co-location assumption on subframe basis(e.g., as shown in TABLE 12 above).

Various embodiments provide linking of DM-RS resources and the CSI-RSresources. The RRC signaling structure may be signaled to indicate howthe DM-RS resources and the CSI-RS resources are linked. The non-zeropower CSI-RS resource may include, for example, and without limitation,CSI-RS configuration, subframe configuration, P_(c), AntennaPortsCount,etc. In some embodiments, instead of associating P_(c) with a CSI-RSresource, an alternative design is to associate P_(c) with a CSIprocess.

In one example (i.e., Example 1), signaling provided by the networkentity to indicate the UE the quasi co-location relationship between aDM-RS resource and a CSI-RS resource may have the following exemplarysignaling structure:

CSI process config list {  CSI process config x{ CSI process idX_(CSIRS) (virtual cell ID for CSI-RS) Non-zero power CSI-RS resourceconfig IMR config ...  } ... } DM-RS config list{ DM-RS config 1{ X_(DMRS)(0) (virtual cell ID for DMRS resource y)  ... (e.g. subframeoffset)

List of CSI process IDs (this is the list of CSI-RS resources that canbe quasi co-located with the DM-RS resource y), e.g. {CSI process ID 1,CSI process ID 2}

} DM-RS config 2{ X_(DMRS)(1) (virtual cell ID for DMRS resource y) ...(e.g. subframe offset) List of CSI process IDs (this is the list ofCSI-RS resources that can be quasi co-located with the DM-RS resourcey), e.g. {CSI process ID 3} } }

In variation of the above example (i.e., Example 1a), the exemplarysignaling structure may include:

CSI process config list {  CSI process config x{ CSI process ID CSI-RSresource ID IMR resource ID ...  } ... } CSI-RS resource config list {CSI-RS resource config x { CSI-RS resource id CSI-RS virtual cell id Nonzero-power CSI-RS resource config Non zero-power CSI-RS subframe config... } ... } IMR resource config list { IMR resource config x { IMRresource ID IMR resource config IMR subframe config ... } ... } DM-RSconfig list{ DM-RS config 1{  X_(DMRS)(0) (virtual cell ID for DMRSresource y)  ... (e.g. subframe offset) A CSI-RS resource ID or a listof CSI-RS resource IDs (this is the CSI-RS resource(s) that can be quasico-located with the DM- RS resource y), e.g. {CSI-RS resource ID 1} or{CSI-RS resource ID 1, CSI-RS resource ID 2} } DM-RS config 2{ X_(DMRS)(1) (virtual cell ID for DMRS resource y)  ... (e.g. subframeoffset) A CSI-RS resource ID or a list of CSI-RS resource ids } }

In variation of the above example (i.e., Example 1b), if a CSI-RSresource can be signaled by the network to be quasi co-located with aCRS of a cell, information about the quasi co-located CRS can beincluded in the CSI-RS resource configuration using the followingexemplary signaling structure:

CSI process config list {  CSI process config x{ CSI process id CSI-RSresource id IMR resource id ...  } ... } CSI-RS resource config list {CSI-RS resource config x {  CSI-RS resource id  Non zero-power CSI-RSresource config  Non zero-power CSI-RS subframe config  Indication thatthe CSI-RS resource is quasi co-located with a CRS ... } ... } CSI-RSresource config list { CSI-RS resource config x {  CSI-RS resource id Non zero-power CSI-RS resource config  Non zero-power CSI-RS subframeconfig  Indication that the CSI-RS resource is quasi co-located withserving cell CRS ... } ... } CSI-RS resource config list { CSI-RSresource config x {  CSI-RS resource id  Non zero-power CSI-RS resourceconfig  Non zero-power CSI-RS subframe config  Indication that theCSI-RS resource is quasi co-located with a CRS  CRS cell-ID (optional)... } ... } IMR resource config list { IMR resource config x {  IMRresource id  IMR resource config  IMR subframe config ... } ... } DM-RSconfig list{ DM-RS config 1{  X_(DMRS)(0) (virtual cell ID for DMRSresource y)  ... (e.g. subframe offset) A CSI-RS resource ID or a listof CSI-RS resource IDs (this is the CSI-RS resource(s) that can be quasico-located with the DM- RS resource y), e.g. {CSI-RS resource ID 1} or{CSI-RS resource ID 1, CSI-RS resource ID 2} } DM-RS config 2{ X_(DMRS)(1) (virtual cell ID for DMRS resource y)  ... (e.g., subframeoffset)  A CSI-RS resource ID or a list of CSI-RS resource ids } }

In variation of the above example (i.e., Example 1c), if a CSI-RSresource can be signaled by the network to be quasi co-located with aCRS of a cell, information about the quasi co-located CRS can beincluded in the CSI-RS resource configuration using the followingexemplary signaling structure:

CSI process config list {  CSI process config x{ CSI process id CSI-RSresource id IMR resource id ...  } ... } CSI-RS resource config list {CSI-RS resource config x {  CSI-RS resource id  Non zero-power CSI-RSresource config  Non zero-power CSI-RS subframe config  Cell ID of thequasi co-located CRS ... } ... } CSI-RS resource config list { CSI-RSresource config x {  CSI-RS resource id  Non zero-power CSI-RS resourceconfig  Non zero-power CSI-RS subframe config  Indication that theCSI-RS resource is quasi co-located with serving cell CRS ... } ... }IMR resource config list { IMR resource config x {  IMR resource id  IMRresource config  IMR subframe config ... } ... } DM-RS config list{DM-RS config 1{  X_(DMRS)(0) (virtual cell ID for DMRS resource y)  ...(e.g. subframe offset) A CSI-RS resource ID or a list of CSI-RS resourceIDs (this is the CSI-RS resource(s) that can be quasi co-located withthe DM- RS resource y), e.g. {CSI-RS resource ID 1} or {CSI-RS resourceID1, CSI-RS resource ID 2} } DM-RS config 2{  X_(DMRS)(1) (virtual cellID for DMRS resource y)  ... (e.g. subframe offset)  A CSI-RS resourceID or a list of CSI-RS resource ids } }

In a second example (i.e., Example 2), signaling provided by the networkentity may allow implicit linking of CSI-RS resource parameter valuesand DM-RS resource parameter values using the following exemplarysignaling structure:

CSI process config list { CSI process config x{ CSI process id XCSIRS(virtual cell ID for CSI-RS) Non-zero power CSI-RS resource config IMRconfig ... }  } DM-RS config list{  DM-RS config 1 { List of CSI processIDs (CSI process ID not only indicates quasi co-location association,but also indicates the DM-RS resource values, e.g. the virtual cell IDof DM-RS and the subframe offset (e.g. virtual cell ID of DM-RS resource1 is the same as the virtual cell ID of the CSI-RS associated with theCSI process id), similarly for subframe offset)  e.g. {CSI process ID 1,CSI process ID 2} }  DM-RS config 2 { List of CSI process IDs (CSIprocess ID not only indicates quasi co-location association, but alsoindicates the DM-RS resource values, e.g. the virtual cell ID of DM-RSand the subframe offset (e.g. virtual cell ID of DM-RS resource 2 is thesame as the virtual cell ID of the CSI-RS associated with the CSIprocess ID), similarly for subframe offset) e.g. {CSI process ID 3} } }

In variation of the above example (i.e., Example 2a), the exemplarysignaling structure allowing implicit linking of CSI-RS resourceparameter values and DM-RS resource parameter values may include:

CSI process config list {  CSI process config x{ CSI process id CSI-RSresource id IMR resource id ...  }  } CSI-RS resource config list {CSI-RS resource config x {  CSI-RS resource id  CSI-RS virtual cell id Non zero-power CSI-RS resource config  Non zero-power CSI-RS subframeconfig ... } ... } IMR resource config list { IMR resource config x { IMR resource ID  IMR resource config  IMR subframe config ... } ... }DM-RS config list{ DM-RS config 1 { A CSI-RS resource ID or a list ofCSI-RS resource IDs (CSI-RS resource ID not only indicates quasico-location association, but also indicates the DM-RS resource values,e.g. the virtual cell ID of DM-RS and the subframe offset (e.g. virtualcell ID of DM-RS resource 1 is the same as the virtual cell ID of theCSI-RS associated with the CSI-RS resource id), similarly for subframeoffset)  e.g. {CSI-RS resource ID 1} or {CSI-RS resource ID 1, CSI-RSresource ID 2} } DM-RS config 2 {  A CSI-RS resource ID or a list of CSIresource IDs } }

In various embodiments for EPDCCH DM-RS, an eNB configures a UE (e.g.,by higher-layer signaling, such as RRC) of the quasi co-locationrelationship between the EPDCCH DMRS and a CSI-RS resource. The eNB mayconfigure the quasi co-location relationship of the UE by configuring aCSI resource ID for the EPDCCH. In one example, for EPDCCH DM-RS, theeNB UE-specifically configures a virtual cell ID and a CSI resource ID.When a UE is configured with a virtual cell ID and a CSI resource ID,the UE uses the virtual cell ID for obtaining a scrambling sequence ofthe EPDCCH DMRS, and the UE assumes that the EPDCCH DMRS and CSI RSassociated with the CSI resource ID is quasi co-located.

In another example, for EPDCCH DM-RS, the eNB specifically configures atleast one pair of a virtual cell ID and a CSI resource ID. For example,a UE may be configured with two pairs of a virtual cell ID and a CSIresource ID. Then, the UE tries to blindly detect a DCI in the EPDCCHwith two hypotheses, one with a first pair and the other with a secondpair. When the UE blindly detects a DCI with the first pair ofparameters, the UE utilizes the virtual cell ID of the first pair forobtaining the scrambling sequence of the EPDCCH DM-RS, and the UEassumes that the EPDCCH DM-RS and CSI RS associated with the CSIresource ID of the first pair is quasi co-located. Similarly, when theUE blindly detects a DCI with the second pair, the UE assumes that theEPDCCH DM-RS scrambled with the virtual cell ID of the second pair andCSI-RS associated with the CSI resource ID of the second pair are quasico-located.

In another example, for EPDCCH DM-RS, the eNB specifically configures aCSI resource ID. When a UE is configured with a CSI resource ID, the UEderives a virtual cell ID for deriving the scrambling sequence of theEPDCCH DM-RS out of the CSI-RS configuration indicated by the CSIresource ID, and the UE assumes that the EPDCCH DM-RS and CSI RSassociated with the CSI resource ID is quasi co-located. Here, thederived virtual cell ID can be the same as the virtual cell IDconfigured for CSI-RS associated with the CSI resource ID.

In one embodiment for EPDCCH DM-RS, two CSI resource IDs are separatelyconfigured, one for localized EPDCCH, and the other for distributedEPDCCH. This method could be useful in CoMP scenario 4, where localizedEPDCCHs are transmitted from pico cells for area splitting, anddistributed EPDCCHs are transmitted in an SFN manner. In one specialcase, the DM-RS for localized EPDCCH may be assumed quasi co-locatedwith the DM-RS for the PDSCH in the same subframe. In this case, acommon CSI resource ID may be used for both DM-RSs. In anotherembodiment for EPDCCH DM-RS, a common CSI resource ID is configured fora localized and distributed EPDCCH (e.g., for simplicity).

In another embodiment, a default quasi co-location relationship betweenEPDCCH DMRS and CRS is defined. In this case, unless there is anexplicit configuration by the network, a UE may assume that EPDCCH DM-RSand CRS are quasi co-located. In another embodiment for DMRS ofdistributed EPDCCH, a UE may assume that CRS is quasi co-located withthe EPDCCH. On the other hand, for DMRS of localized EPDCCH, the UE mayassume that a CSI-RS is quasi co-located with the EPDCCH, where theCSI-RS is the one corresponding to a CSI resource ID configured forindicating the quasi co-location information between CSI-RS andlocalized EPDCCH. In another embodiment, the DMRS of EPDCCH can beflexibly mapped to any of CRS and/or CSI-RS (e.g., by configuring a CSIresource ID for the DMRS of EPDCCH). The CSI resource ID 0 can be usedfor CRS and positive-integer CSI resource IDs may be used for CSI-RS.

FIG. 8 illustrates a process for identifying quasi co-located referencesignal ports by a UE in accordance with various embodiments of thepresent disclosure. For example, the process depicted in FIG. 8 may beperformed by the receiver 410 in FIG. 4. The process may also beimplemented by the UE 505 in FIG. 5.

The process starts with the UE receiving downlink control information(step 805). For example, in step 805, the downlink control informationis higher-layer signaled (e.g., via RRC) or dynamically signaled (e.g.,PDCCH or EPDCCH).

The UE then identifies a CSI-RS resource that is quasi co-located with aDM-RS port assigned to the UE (step 810). For example, in step 810, theUE may identify the CSI-RS port and/or DM-RS port assignments and thenidentify an indication of the quasi co-location assumption from thecontrol information according to embodiments described above.Additionally, the UE may identify a CRS port(s) associated with theCSI-RS port(s) as quasi co-located with the assigned DM-RS port inresponse to identifying that the CSI-RS resource is quasi co-locatedwith the assigned DM-RS resource.

The UE then identifies large scale properties for the DM-RS port (step815). The CSI-RS port being quasi co-located with the assigned DM-RSport means that at least some of the large scale properties for theDM-RS port can be inferred from the large scale properties for theassigned CSI-RS port and vice versa. For example, in step 815, the UEmay derive the large scale properties for the DM-RS port based on largescale properties for the assigned CSI-RS port. The derived large scaleproperties include, for example, and without limitation, one or more ofa Doppler shift, a Doppler spread, an average delay, or a delay spread.

The UE then performs at least one of channel estimation, timesynchronization, or frequency synchronization (step 820). For example,in step 820, the UE may perform the channel estimation using theidentified large scale properties for the DM-RS and/or the CSI-RS port.The identified large scale properties may be used in addition to or inlieu of measured properties to improve the channel estimation.Additionally or alternatively, the UE may use the identified large scaleproperties for timing and/or frequency synchronization.

FIG. 9 illustrates another process for identifying quasi co-locatedreference signal ports by a UE in accordance with various embodiments ofthe present disclosure. For example, the process depicted in FIG. 9 maybe performed by the receiver 410 in FIG. 4. The process may also beimplemented by the UE 505 in FIG. 5.

The process begins with the UE receiving downlink control information(step 905). For example, in step 905, the downlink control informationmay be higher-layer signaled (e.g., via RRC).

The UE then identifies a CRS port that is quasi co-located with a CSI-RSport configured for the UE (step 910). For example, in step 910, the UEmay identify the CSI-RS port and/or CRS port assignments and thenidentify an indication of the quasi co-location assumption from thecontrol information according to embodiments described above. In oneparticular example, the UE may identify, from the downlink controlinformation, a cell identifier associated with one or more CRS ports,one or more CSI-RS ports associated with a CSI-RS resource configuredfor the UE, and then determine that the one or more identified CRS portsare quasi co-located with the one or more identified CSI-RS portsassociated with a CSI-RS resource configured for the UE.

The UE then identifies large scale properties for the CSI-RS port (step915). The CRS port being quasi co-located with the configured CSI-RSport means that at least some of the large scale properties for theCSI-RS port can be inferred from the large scale properties for the CRSport and vice versa. For example, in step 915, the UE may derive thelarge scale properties for the CSI-RS port based on large scaleproperties for the configured CRS port and vice versa. The derived largescale properties include, for example, and without limitation, one ormore of a Doppler shift, a Doppler spread, an average delay, or a delayspread.

The UE then performs at least one of channel estimation, timesynchronization, or frequency synchronization (step 920). For example,in step 920, the UE may perform the channel estimation using theidentified large scale properties for the CRS port and or the CSI-RSport. The identified large scale properties may be used in addition toor in lieu of measured properties to improve the channel estimation.Additionally or alternatively, the UE may use the identified large scaleproperties for timing and/or frequency synchronization.

Although FIGS. 8 and 9 illustrate examples of processes for identifyingquasi co-located reference signal ports by a UE, various changes couldbe made to FIGS. 8 and 9. For example, while shown as a series of steps,various steps in each figure could overlap, occur in parallel, occur ina different order, or occur multiple times.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

What is claimed is:
 1. An apparatus for communication in a communicationsystem, comprising: a controller; and a transceiver configured to:receive first information indicating at least two reference signal (RS)resources for at least two RSs, second information for providing quasico-location relationships between RSs associated with the at least twoRS resources and demodulation reference signal (DMRS) ports, and thirdinformation indicating a cell index to which a RS resource is applied,receive control information for scheduling of downlink data channel, thecontrol information including information indicating which RS resourcefrom among the at least two RS resources indicated by the firstinformation is quasi co-located with DM-RS ports related to the downlinkdata channel, and receive a data channel signal scheduled by the controlinformation, based on the first information, the second information, andthe third information, wherein at least one DMRS port of the downlinkdata channel is quasi co-located with at least one RS in the RS resourceindicated the control information.
 2. The apparatus of claim 1, whereinthe at least one DMRS port and the at least one RS are quasi co-locatedmeans that large scale properties for the at least one DMRS port can beinferred from the large scale properties for the at least one RS, andthe large scale properties include at least one of a Doppler shift, aDoppler spread, an average delay, and a delay spread.
 3. The apparatusof claim 1, wherein the controller is further configured to assume theat least one DMRS port and the at least one RS are quasi co-located, iffourth information is received.
 4. An apparatus for communication in acommunication system, comprising: a controller; and a transceiverconfigured to: transmit first information indicating at least tworeference signal (RS) resources for at least two RSs, second informationfor providing quasi co-location relationships between RSs associatedwith the at least two RS resources and demodulation reference signal(DMRS) ports, and third information indicating a cell index to which aRS resource is applied, transmit control information for scheduling ofdownlink data channel, the control information including informationindicating which RS resource from among the at least two RS resourcesindicated by the first information is quasi co-located with DM-RS portsrelated to the downlink data channel, and transmit a data channel signalscheduled by the control information, based on the first information,the second information, and the third information, wherein at least oneDMRS port of the downlink data channel is quasi co-located with at leastone RS in the RS resource indicated the control information.
 5. Theapparatus of claim 4, wherein the at least one DMRS port and the atleast one RS are quasi co-located means that large scale properties forthe at least one DMRS can be inferred from the large scale propertiesfor the at least one RS port, and the large scale properties include atleast one of a Doppler shift, a Doppler spread, an average delay, and adelay spread.
 6. The apparatus of claim 4, wherein the at least one DMRSport and the at least one RS are quasi co-located if fourth informationis received.
 7. A method for communication in a communication system,the method comprising: receiving first information indicating at leasttwo reference signal (RS) resources for at least two RSs, secondinformation for providing quasi co-location relationships between RSsassociated with the at least two RS resources and demodulation referencesignal (DMRS) ports, and third information indicating a cell index towhich a RS resource is applied; receiving control information forscheduling of downlink data channel, the control information includinginformation indicating which RS resource from among the at least two RSresources indicated by the first information is quasi co-located withDM-RS ports related to the downlink data channel; and receiving a datachannel signal scheduled by the control information, based on the firstinformation, the second information, and the third information, whereinat least one DMRS port of the downlink data channel is quasi co-locatedwith at least one RS in the RS resource indicated the controlinformation.
 8. The method of claim 7, wherein the at least one DMRSport and the at least one RS are quasi co-located means that large scaleproperties for the at least one DMRS port can be inferred from the largescale properties for the at least one RS, and the large scale propertiesinclude at least one of a Doppler shift, a Doppler spread, an averagedelay, and a delay spread.
 9. The method of claim 7, wherein the atleast one DMRS port and the at least one RS are quasi co-located, iffourth information is received.
 10. A method for communication in acommunication system, the method comprising: transmitting firstinformation indicating at least two reference signal (RS) resources forat least two RSs, second information for providing quasi co-locationrelationships between RSs associated with the at least two RS resourcesand demodulation reference signal (DMRS) ports, and third informationindicating a cell index to which a RS resource is applied; transmittingcontrol information for scheduling of downlink data channel, the controlinformation including information indicating which RS resource fromamong the at least two RS resources indicated by the first informationis quasi co-located with DM-RS ports related to the downlink datachannel; and transmitting a data channel signal scheduled by the controlinformation, based on the first information, the second information, andthe third information, wherein at least one DMRS port of the downlinkdata channel is quasi co-located with at least one RS in the RS resourceindicated the control information.
 11. The method of claim 10, whereinthe at least one DMRS port and the at least one RS are quasi co-locatedmeans that large scale properties for the at least one DMRS can beinferred from the large scale properties for the at least one RS port,and the large scale properties include at least one of a Doppler shift,a Doppler spread, an average delay, and a delay spread.
 12. The methodof claim 10, wherein the at least one DMRS port and the at least one RSare quasi co-located if fourth information is received.